Infrared Spectroscopy for the Analysis of Bioactive Analytes in Wheat: A Proof-of-Concept Study

This study compared the performance of near-infrared spectroscopy (NIRS) and mid-infrared spectroscopy (MIRS) for the prediction of moisture, protein, total phenolic content (TPC), ferric reducing antioxidant potential (FRAP) and total monomeric anthocyanin (TMA) content in 65 samples of Australian wheat flour. Models were constructed on 50 of the wheat samples, with the 15 remaining samples used as a dependent test set. NIRS showed excellent results for the prediction of protein content (R2test = 0.991; RMSEP = 0.22% w/v) and acceptable to good results for TPC (R2test = 0.83; RMSEP = 3.9 mg GAE/100 g), FRAP (R2test = 0.92; RMSEP = 5.4 mg TE/100 g) and moisture content (R2test = 0.76, RMSEP = 0.62% w/v). Similarly, MIRS showed the best results for protein prediction (R2test = 0.93, RMSEP = 0.62% w/v) and acceptable results for moisture content (R2test = 0.83, RMSEP = 0.65% w/v), FRAP (R2test = 0.83, RMSEP = 7.0 mg TE/100 g) and TPC (R2test = 0.73, RMSEP = 5.6 mg GAE/100 g). However, the TMA content could not be predicted. Finally, moving window analysis was conducted to determine the optimum wavelength ranges for predicting selected analytes. On average, this improved RMSECV values by an average of 18–20% compared to the corresponding full wavelength models, when using the same component selection method. The results confirm that infrared spectroscopy may be useful for the real-time quantitation and/or screening of key quality parameters in wheat, such as protein, TPC and antioxidant capacity.